This application, and the innovations and related subject matter disclosed herein, (collectively referred to as the “disclosure”) generally concern microphone-based orientation detectors and associated techniques. More particularly but not exclusively, this disclosure pertains to sensors (also sometimes referred to as detectors) configured to determine an orientation of a device relative to a speaker's mouth, with a sensor configured to determine an orientation based in part on a difference in spectral power between two microphone signals being but one particular example of disclosed sensors.
Some commercially available communication handsets have two microphones. A first microphone is positioned in a region expected to be near a user's mouth during use of the handset, and the other microphone is spaced apart from the first microphone. With such an arrangement, the first microphone is intended to be positioned to receive the user's utterances directly, and the other microphone receives a comparatively attenuated version of the user's utterances, allowing a signal from the other microphone to be used as a noise reference.
Two-microphone arrangements as just described can provide a much more accurate noise spectrum estimate as compared to estimates obtained from a single microphone. With a relatively more accurate estimate of the noise spectrum, a noise suppressor can be used with relatively less distortion to the desired signal (e.g., a voice signal in context of a mobile communication device).
However, despite such benefits of two-channel noise suppression, if the first microphone is moved away from the user's mouth, as when the handset is repositioned during use, then the accuracy of the spectral noise estimate can decrease, as the first microphone can receive a more attenuated version of the speech signal. Consequently, the reference microphone signal can include relatively more voice components relative to the first microphone, leading to voice distortion because there is less spectral separation between the microphone transducers when the user speaks.
Therefore, a need exists for orientation detectors configured to detect when a microphone has been moved away from a user's mouth. In addition, a need exists for speech enhancers compatible with a wide range of handset use positions. As well, a need exists for improved noise-suppression systems for use in mobile communication handsets.